Dermatophilosis and dermatophytosis are two common skin conditions often confusedDermatophilosis and dermatophytosis are two somewhat similar and all too common conditions of the skin of horses. These are two good words, in that I know very few six-syllable words that rhyme. Unfortunately, I write little poetry and when I do I usually stick with the June-moon and blue-you genres (hence you are unlikely to see a volume of my collected works), and the knowledge of long, rhyming words is, therefore, not much benefit to me. For that reason, among others, we will translate these terms to common language.
Dermatophilosis is rain scald; dermatophytosis is ringworm. Rain scald and ringworm do not rhyme and, even if they did, it would be a real challenge to create a poem around them.

Dermatophilosis
Rain scald is caused by an actinomycete and occurs in a variety of species. For our purposes, though, we will describe it only as it affects the horse. It is usually seen in the fall and winter and is most often associated with times of increased rainfall. Stress (constant exposure to cold and wet) and ectoparasites (house flies, stable flies) are also involved; stress reduces resistance, and ectoparasites provide a means of access for the infective organism via bites in the skin. Stabled, non-stressed horses may also contract the condition by way of contaminated clippers or grooming materials.
The chief signs of rain scald are varyingly sized clumps of matted hair, under which are scabs. The undersides of these scabs hold pockets of yellowish to greyish pus, and the areas may be painful to the touch. The appearance and history are usually diagnostic, but the causative agent may be demonstrated in cultures.
Rain scald is self-limiting; i.e., if you leave it alone, it will eventually go away. This is not fair to the horse, though, so something needs to be done. The most important part of the treatment is the removal of the scabs. As the areas are often painful, the horse may not fully appreciate your efforts along these lines, so soaking them (the scabs, not the horses) in a warm, iodine-based shampoo accomplishes two things: (1) the scabs and matted hair soften and are more easily removed; and (2) the iodine shampoo kills the causative organism. Once the scabs are gone, the iodine shampoos should be continued for several days, until there are no wet spots remaining where the scabs were.
Some cases of rain scald are extremely severe, however, and for these the use of systemic antibiotics or fungicides is indicated, even though the organism is neither bacterium nor fungus. Your veterinarian will decide the agent of choice.
Possibly more important than any of the above, though, is the need to keep the animal dry and stress- and ectoparasite-free until full recovery. This is also the key to future prevention.

Dermatophytosis
Ringworm is caused by any one of several species of fungi, and there is a great range of susceptibility among horses. Some seemingly can wallow in a vat of the organisms and never have a problem, while others suffer extensive hair loss if a single ringworm fungus wafts through the county.
Dirty, damp, warm conditions are predisposing factors, and ringworm can be spread by contaminated clippers, brushes, saddle pads, etc., as well as by direct contact with other infected animals or people.
The signs are diagnostic: multifocal areas of alopecia (hair loss), radiating outward from a central point, along with scaliness of the area and, in some cases, pruritis (itching). Unlike rain scald, where the organism is under the scab in the middle, the ringworm organism is most abundant at the periphery of the lesions. If a culture is desired, it should be taken from these areas.
As with rain scald, ringworm is self-limiting. It will run its course in six-to-12 weeks, but during this time the horse is contagious, so it is important to try to shorten the natural course. This may be done easily: (1) clip the areas (disinfect the clippers before and after use); (2) bathe the horse with an iodine-based shampoo and let the shampoo remain on the skin for 15-to-30 minutes before rinsing thoroughly; and (3) repeat the baths daily for four or five days and then twice a week until the infected areas heal. Systemic antifungal agents may be used for extensive cases.
Sunlight and fresh air are important in the control of ringworm. A major factor in control of spread and prevention is the disinfection of your equipmentclippers, brushes, halters, blankets, pads, saddles, stalls, etc.whatever your horses contact. Actually, this is a common sense procedure which should be done on a routine basis anyhow.
The accompanying table summarizes rain scald and ringworm. Although both conditions are promoted by inattention or neglect, they may happen in spite of the best of care. Proper, early care will prevent severity and spread.